For basic questions about limits, continuity, derivatives, differentiation, integrals, and their applications, mainly of one-variable functions.
Calculus is the branch of mathematics studying the rate of change of quantities, which can be interpreted as slopes of curves, and the lengths, areas and volumes of objects.
Calculus is divided into differential and integral calculus, which are concerned with derivatives
$$\frac{\mathrm{d}y}{\mathrm{d}x}= \lim_{\Delta x \to 0} \frac{\Delta y}{\Delta x}$$
and integrals
$$\int_a^b f(x)\,\mathrm{d}x = \lim_{\Delta x \to 0} \sum_{k=0}^n f(x_k)\ \Delta x_k,$$
respectively.
